Even as it champions the Paris climate agreement, Japan - the world's fifth-biggest carbon emitter - continues its massive reliance on coal and natural gas, putting it out of step with the rest of the Group of Seven bloc and even South Korea.

Coal is seen by Japan's powerful industry ministry as an important part of the country's energy mix after the closure of nuclear reactors in the wake of the 2011 Fukushima disaster.

"It doesn't matter if they are highly efficient or not, power stations using coal are seen outdated as EU (European Union) and other countries are moving away from them," Environment Minister Kouichi Yamamoto told Reuters in an interview on Thursday.

"We are against coal-fired power plants, but the issue isn't whether we are for or against it, but that there may come a time when they will no longer be accepted by the world at large," he said.

Coal now accounts for about 31 percent of Japan's power generation mix. Over the next decade, companies plan to build 41 new coal-fired power stations, according to data from government and companies.

"If all those plants are built, it will become a major obstacle for Japan's 2030 target to cut emissions," said Yamamoto.

Under the Paris deal, Japan has pledged to trim its carbon emissions by 26 percent in 2030 from 2013 levels.

The ministry estimates that Japan's emissions could exceed its 2030 target by 70 million tonnes if all the coal power plants were built.

Yamamoto said carbon pricing can help Japan hit its further target to slashing emissions by 80 percent by 2050.

"By 2050, we don't aim to lower carbon, but we aim to exit from carbon. Carbon pricing is the most efficient tool to help us achieve the 2050 goal," Yamamoto said.

The environment ministry recently set up a panel to discuss an appropriate carbon pricing. But the industry ministry has opposed it, claiming Japan already has high taxes on oil and coal, along with environment tax.

"We are not saying that we should implement carbon pricing, but we are saying we should talk and think about how Japan can come up with our own model based on other countries' experiences," he said.

Yamamoto said he was disappointed at the recent decision of the United States to withdraw from the Paris Climate Agreement. He was involved in the adoption of the Kyoto Protocol in 1997 which the U.S. did not ratify.

"The Kyoto Protocol was mainly to enhance developed countries to combat global warming, but the Paris climate pact is for all countries and underlines a big advancement," he said.

"Therefore, the U.S. withdrawal this time has a much bigger implication than that from the Kyoto Protocol." (Reporting by Yuka Obayashi and Ami Miyazaki; Editing by Aaron Sheldrick and Manolo Serapio Jr.)

“To save the environment and to fight climate change, my government has planned a major campaign. By 2022, we want to generate 175 GW of renewable energy. In the last three years, we have already achieved 60 GW or around one-third of this target,” he said.